The present invention relates to a cooling device and, more particularly, to a device for cooling motor vehicle wheels equipped with disc brakes located on the wheels between wheel centers and a cover plate, with rotors of the disc brakes being mounted to a wheel flange of a wheel hub by a pot-shaped mounting portion which delimits a radially annular space open toward the cover plate, and with the cover plate being provided with openings through which a cooling air stream may enter the wheel space accommodating the brake, and openings provided in the wheel center near the rim through which air may escape from an external annular space defined between the brake and the center, which annular space communicates, by way of a space between the rim and the brake, with an annular space delimited, in an axial direction, by the space between the rim and the brake and the cover plate.
A cooling arrangement of the aforementioned type has been proposed in, for example, Offenlegungsschrift 24 32 728, wherein a disc brake, constructed as a so called full disc brake, includes a pot-shaped mounting member or part integrally formed with a brake housing, with the mounting part being arranged so as to rotate with a hub of the vehicle wheel.
In the above-noted proposed arrangement, a cooling air stream entering through openings in a cover plate in approximately an axial direction, encounters an inner area of a ribbed section of the brake housing, as viewed in a radial direction with a rotation of the cooling air stream being immediately forced away in the radial direction from the point of entry. The cover plate, also of a pot-shaped construction, delects the cooling air stream over a peripheral area of the brake housing and the brake disc and into an outer annular space which is essentially delimited by the wheel center and an outer portion of the brake housing from where the air, possibly considerably heated in the brake chamber, flows out through an outlet opening in the wheel center. Thus, a direct heat transmission from parts of the brakes or wheels, considerably heated during a brake application, takes place only through the surfaces of those parts or components of the brakes which, as viewed in a radial direction, are disposed outside of the pot-shaped mounting part or member; whereas, the parts or components of the wheels which are disposed inside the pot-shaped mounting part or member, i.e., essentially the hub and wheel bearing, experience practically no cooling effects. Consequently, the inner wheels parts in particular are heated to a disporportionate degree especially, for example, during a prolonged braking application when descending a long hill thereby causing a drastic increase in the wear on the wheel bearings and sliding seals. Furthermore, the cooling air stream, already considerably heated in the space between the cover plate and the brake, after the deflection, is guided over the peripheral portions of the brake directly to the outlet openings of the outer annular space and, consequently, cannot produce any significant cooling in the annular space.
In an attempt to nevertheless achieve a more uniform bilateral cooling of the brake, it has been proposed to provide additional inlet openings for cooling air flowing inwardly from the outside of the wheel at a slight radial distance from the wheel axis; however, in order to compensate for the weakening of the wheel occasioned by the provision of such additional openings, the wheel center must have an especially solid construction in an area of the wheel center which is near the heavily stressed hub of the wheel.